The PPA contains a version of GTK+ with Mir support, fixes for libraries that assume you are running in X and a few select applications patched so they show in Unity 8.

The Mir backend currently on the wip/mir branch in the GTK+ git repository. We will keep developing it there until it is complete enough to propose into GTK+ master. We have updated jhbuild to support Mir so we can easily build and test this backend going forward.